Cross-sectional and longitudinal analyses of the association between lung function and exercise capacity in healthy Norwegian men

Background: It is widely accepted that exercise capacity in healthy individuals is limited by the cardiac function, while the respiratory system is considered oversized. Although there is physiological, age-related decline in both lung function and physical capacity, the association between decline in lung function and decline in exercise capacity is little studied. Therefore, we examined the longitudinal association between lung function indices and exercise capacity, assessed by the total amount of work performed on a standardized incremental test, in a cohort of middle-aged men. Methods: A total of 745 men between 40 and 59 years were examined using spirometry and standardized bicycle exercise ECG test within "The Oslo Ischemia Study," at two time points: once during 1972-1975, and again, approximately 16 years later, during 1989-1990. The subjects exercise capacity was assessed as physical fitness i.e. the total bicycle work (in Joules) at all workloads divided by bodyweight (in kg). Results: Higher FEV1, FVC and PEF values related to higher physical fitness at both baseline and follow-up (all p values < 0.05). Higher explanatory values were found at follow-up than baseline for FEV1 (r(2) = 0.16 vs. r(2) = 0.03), FVC (r(2) = 0.14 vs. r(2) = 0.03) and PEF (r(2) = 0.13 vs. r(2) = 0.02). No significant correlations were found between decline in physical fitness and declines in FEV1, FVC or PEF. Conclusions: A weak association between lung function indices and exercise capacity, assessed through physical fitness, was found in middle-aged, healthy men. This association was strengthened with increasing age, suggesting a larger role for lung function in limiting exercise capacity among elderly subjects. However, decline in physical fitness over time was not related to decline in lung function.